<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
         .box{
        width:400px;
        height:400px;
        background:salmon;
    }
    .box1{
        width:200px;
        height:200px;
        background:seagreen;
    }
    .box2{
        width:100px;
        height:100px;
        background:darkgoldenrod;
    }
    </style>
   
</head>
<body>
    <div class="box">
        <div class="box1">
            <div class="box2">

            </div>
        </div>
    </div>
</body>
</html>